1. Field of the Invention
This invention is related to security doors and more particularly to the type of security doors having double cylinder key locks to permit the locking and unlocking of the security doors from either the inside or outside of buildings.
2. Description of Related Art
Grille type metal security doors are commonly used in combination with prime outer doors to enhance the security of residential and commercial buildings. The security doors are generally installed forward of and in spaced apart relationship to the prime outer doors and substantially fill the openings of the prime outer doors. They are characterized by assemblies of welded tubular or solid rod-like members in the form of open grille-type structures. As used herein, the term "security door" includes a grille-type structure made primarily from metal having open spaces between the grille members, commonly called a security door gate or guard, as well as a grille-type structure made of metal and glass having spaces between the grille members spanned by glass, commonly called a security storm door.
It is a common practice with security doors to maximize their effectiveness by incorporating key locks which allow users the alternative of locking or unlocking security doors from the inside or outside so that they can be made operational in occupied as well as unoccupied buildings.
The common means for providing this feature is the double cylinder mortise type key lock which can be actuated with a key from either the forward or rearward side of the lock. By way of example is the so-called double cylinder dead bolt key lock having lock cylinders and keyways on the forward and rearward sides of the lock.
Although the foregoing practice for maximizing security door effectiveness is in common use, it violates most local building codes and is fraught with risk to occupants of buildings for the reason that keys are seldom readily accessible to all of the occupants during emergency situations for the unlocking of security doors. It will be appreciated that this risk is greatest to sleeping occupants during the hours of the night.
Inasmuch as there are spaces between the grille bars of security doors, when keys are left engaged in the rear lock cylinders of existing doors, either inadvertently or intentionally, to insure their immediate availability for emergency egress from a building, the security of the building is placed in jeopardy because the keys are in plain view through the grille bars of the doors and accessible to persons attempting to unlawfully enter the building.
With the foregoing in mind, an important need clearly exists to provide an immediate available means to occupants of a building, having double cylinder key lock security doors, for unlocking said doors during emergency egress from the building without diminishing the current level of security which is provided by the security doors.